Education, especially in elementary forms, is undertaken not so much to make the student an expert in the field as to give the student sufficient proficiency to understand the use of the technique, whether in the so-called useful arts of arithmetic, writing, manual training, physical training, and others, or in the arts of painting, sculpture, poetry, dance, and others, which are sometimes referred to as decorative, or fine, arts. Among the fine arts, two-dimensional graphic expression has been assisted by the availability of a wide variety of materials suitable for use by students of every age and level of expertise. Sculpture, in contrast, has not been so fortunate. Clay, from which three-dimensional forms can be produced, is relatively easily procured by students at all levels, but solid stone in a form that can be carved by even the youngest student is not. Clay allows the correction of mistakes and changing of thought, since clay sculptures are produced by adding soft clay to whatever is already there. Stone, which is carved only by removal of material that, once gone, cannot be replaced, cannot be corrected nearly as easily. There is a discipline in stone unmatched by the rectifiable modeling permitted by clay. However, clay is much used by modern sculptors, even those of great artistic ability, who employ assistants who are less creative but are sufficiently manually proficient to produce a final work of art in stone according to the clay prototype created by the artist. It has been said that it may be this very lack of experience in working with stone that makes it difficult for the modern sculptor to become a thorough master of the art, thinking naturally in stone rather than in clay.
A characteristic of a stone sculpture, equal in importance to the disciplines of forethought and accuracy imposed on the sculptor, is the permanence of the finished work of art. No gentle force, whether of impact, wind, or water, should be able to make an easily observable effect upon it in a measurable span of time.